This invention relates to a handled plastic container in which the container is formed by blow molding a preform and the handle is separately formed and then connected to the container during the container forming process.
Plastic containers for holding liquids including beverages and other domestic liquids are in wide spread use. During the 1980""s plastic largely replaced glass as the material of first choice for the packaging of carbonated soft drinks. Plastics such as polyethylene terephthalate (PET) offer significant savings when compared with glass in packaging such products. Plastic is lighter than glass and plastic bottles are cheaper to make and cheaper to transport than glass bottles. In addition, there are clear safety advantages when using plastic given the inherent problems with breakages when using glass. Plastic containers are also in wide use for products such as detergents and fruit juices. Such products are generally packaged in one or two litre containers with relatively large outlet openings. For ease of pouring, containers such as those made from PVC often include a handle. In the past, the handle in plastic containers formed by extrusion blow molding has been provided by blow molding a hollow and integral handle portion into the container side wall.
Given the constraints of container design, such handles are generally quite broad and often leave little room for one to firmly grasp the inside of the handle. Special molds are required in the production of such bottles, they are more difficult to blow mold than a non handled bottle and there are difficulties with stress concentrations leading to possible container failure in the areas near the junction of the handle with the rest of the container. In addition, it has not been generally possible to economically produce such handled bottles from synthetic polyesters such as PET. To extrusion blow mold PET it would be necessary to use a resin having a high intrinsic viscosity, i.e. well over 1.0. Such containers would not have the same degree of side wall orientation as a container stretch blow molded from the preform.
If an integral handle was formed in a PET container formed from a preform, a special cutting tooling would be required to remove the flashing from between the container side wall and the integrally formed handle due to the high orientation of the material.
An alternative is the use of a separate handle joined to the container. If a separate handle is utilized, it is possible to injection mold a handle which is narrower and thinner than the integral handles of the previously described blow-molded containers, and if adequately attached to the container, such handle designs are more effective and easier to use.
Various attempts have been made to attach separate handles to blow molded containers formed from preforms but these have not been altogether successful. One difficulty has been inadequate engagement of the handle with the blow molded container. For example, it has previously been proposed that such handles be connected to the plastic container by blow molding the walls of the container around retaining portions provided at the respective ends of the handle. For example, reference is made to Australian patent 637,696. In processes where the handle is pre-engaged with the preform prior to positioning the combination into the blow mold, there are problems in automating the whole process. The need to interconnect the handle with the preform prior to introducing the combination into the blow mold complicates the manufacturing process and can slow it down. This is especially so if the interconnection process occurs in a different direction to the direction of insertion of the combination into the blow mold.
It is an object of the present invention to provide a method of securing a separate handle to a plastic blow molded container which enables relatively rapid manufacture and which leads to the production of a handled bottle where the handle is firmly secured.
In one embodiment, the invention utilises a molded external flange which is not subject to stretching during the blow molding process and which provides a rigid support, against which an upper end of the handle is held by a portion of the side wall of the container once the preform has been blown.
This embodiment thus achieves the desired object by positioning a preform and a handle into a blow mold and thereafter stretch blow molding the preform in such a way as to sandwich the upper end of the handle between a portion of the side wall of the formed container and a substantially flat underside of a molded external flange located on the neck of the preform. This simplifies the construction of the handle and preform, as well as simplifying the positioning of the preform and handle during blow molding to thus reduce the overall cost of manufacture, while providing a secure attachment.
More particularly, in accordance with one embodiment of the present invention there is provided a method of manufacturing a handled plastic container which includes the steps of:
(a) positioning in an open blow mould a synthetic plastics preform which includes an external flange with a substantially flat underside face, and a handle which includes an upper end with a substantially flat abutment surface;
(b) closing the blow mould and stretch blow moulding the preform beneath the flange to form a container, wherein a sidewall portion of the preform is expanded so as to sandwich the upper end of the handle between a portion of the sidewall of the formed container and the flange with the substantially flat upper abutment surface and underside face being pressed together so as to fixedly connect the handle to the blown container.
Preferably the preform and handle are brought together into position where the upper end of the handle is adjacent to the underside of the external flange by relative movement of the preform and the handle towards each other along a first path which is substantially perpendicular to a longitudinal axis of the preform.
Most preferably, the preform and handle are brought together into this position prior to their introduction into the blow mould. In such case, it is preferred that the handle and preform once brought together be introduced into the blow mould together along a second path which is also substantially perpendicular to the longitudinal axis of the preform. The first and second paths may conveniently be in the same plane so that the handle and preform may be brought together and conveyed into the open blow mould by movement along a path which has no abrupt changes in direction.
Generally, the method of the invention is used with blow moulding equipment which requires that the preform be pre-heated before introduction into the blow mould to a temperature at which it may be stretched and blow moulded (e.g., in the glass transition range). Therefore, generally the preform is hot and the handle is cold when the two are positioned in the mould.
It is preferred that the preform and the handle be unconnected when positioned in the open blow mould. However, in one embodiment of the invention further described below where the handle is attached to the container only at its upper end, it is preferred that the upper end of the handle be broad enough to clip around the preform immediately beneath the external flange.
Preferably, the upper end of the handle also includes retaining means such that upon expansion of the sidewall of the preform, the retaining means is caused to interconnect with a portion of the formed container. Most preferably, the retaining means is adapted to be integrated with a portion of the wall of the container. The retaining means may take a number of different configurations. For example, it can comprise a downwardly facing projection, such as a lug or hook. In such an embodiment, the downwardly extending projection is adapted to firmly integrate and interconnect with the plastic material forming that part of the side wall of the blown container adjacent the external flange.
The preform may be of any suitable shape for forming a container. In some cases, it is preferred that the body of the preform be wider than the external flange. This is particularly so for the manufacture of larger containers. It is preferred that the upper end of the handle include a support platform with a curved front face which is shaped to conform against the outer surface of the preform wall below the flange, and a flat top face which lies against the flat underside surface of the external flange.
The external flange on the preform should resist vertical (upwards) detachment of the handle and the upper end of the handle should be pressed against the underside of the external flange so to resist horizontal detachment. The method of the present invention enables one to produce a handled plastic bottle in which the upper end of the handle is fixedly connected to the blown container at a location immediately beneath the external flange. The other end of the handle does not need to be connected to the container and in such an embodiment, the depending gripping portion terminates at an unconnected free end.
In an alternative embodiment, the lower end of the handle may include lower retaining means also adapted to be integrated within a portion of the wall of the formed container. The handle and the preform may be positioned within the blow mould simultaneously and may be positioned in the mould by a single transfer arm which holds them both. The handle and preform do not need to be exactly positioned with the upper end of the handle in direct abutment with the underside of the external flange of the preform. There may be a small gap between the two. If there is a small gap between the two after they have been introduced into the open blow mould, this can be rectified after the blow mould has been closed. The blow mould may be shaped so to allow the preform to be moved downwardly from its original position within the blow mould by a distance of between about I to 4 mm so to push the preform so that there is direct abutment between the upper end of the handle and the underside face of external flange. Conveniently, the preform may be pushed down by the blow nozzle intended for use in introducing the high pressure gas into the preform to cause stretch blow moulding.
Alternatively, the preform and handle may be separately introduced into the open blow mould on separate transfer arms, each moving in a substantially horizontal plane. The handle may be inserted into the blow mould marginally earlier or later than the preform and the side wall of the preform and the upper end of the handle may be respectively shaped so that the preform may slide across the top of the handle when being positioned adjacent to the handle in the blow mould.
Most preforms used on the commercial stretch blow moulding of containers include a flange beneath the container neck finish. This flange (often referred to as the xe2x80x9csupport ledgexe2x80x9d) has many purposes including the mechanised transfer of the preform to and from a blow mould and the support of the preform within the blow mould during the introduction of high pressure gas to blow mould the container. Such preforms may be used in the method of the present invention.
Preferably, the upper end of the handle includes a support platform having a curved front face shaped to follow the geometry of the preform immediately beneath the external flange. Such a curved face assists in the positioning and location of the handle adjacent to the preform. Where a curved face is provided, the inner diameter of the curved face should match the outside diameter of the preform. The arc length of the face may vary but it is found that it is easier to insert the handle into conventional blow molding tools when the arc is relatively short (between 5 to 15xc2x0). However, in cases where the blow molding apparatus can accommodate a broader face it can be desirable for the arc length to be larger. As it is preferred that the handle and preform be brought together along a path substantially perpendicular to the longitudinal axis of the preform, the arc length of the curved face cannot be significantly greater than 180xc2x0. If the handle is made from a resilient plastics material the arms of the curved face can extend around an arc length of up to about 220xc2x0-the preform being capable of being pushed through the opening between the arms with the arms thereafter clipping around the preform body. This arrangement provides more secure attachment of the upper end of the handle to the container once blown and is preferred in cases where the lower end of the handle is not to be attached to the container.
In a particularly preferred embodiment the handle includes a support platform with a front face shaped to follow the geometry of the preform immediately beneath the flange and a retaining means is spaced below the support platform and extends toward the preform such that plastics material is molded about the retaining means to thereby lock the retaining means within the wall of the plastic container. The spacing between the support platform and retaining means will generally allow plastics material to pass between the retaining means and support platform adjacent the upper surface of the retaining means and the retaining means preferably increases in vertical dimension toward the preform. The retaining means may include coacting upper and lower tabs which vertically diverge and extend toward the preform to provide increasing dimensions. The molding of plastic material on opposite sides of the coacting tabs locks the handle with the container wall. The lower of the tabs preferably extends downward so that plastic is molded adjacent its outer side.
In the embodiment of the invention where the handle includes a curved face which follows the geometry of the preform the handle may also include a recessed portion adjacent to the curved face which comprises one or more ribs. In such arrangement, when the preform is blown the portion of the preform immediately adjacent the curved face will expand into the recessed portion but less so into those areas comprising ribbing. As a consequence, once the bottle is blown the ribs in the recessed portion will be located within small indentations on the container and the ribs and indentations will thus co-operate to resist rotational movement of the handle. Alternatively, or in addition, the blow mould may incorporate small cavities positioned to be adjacent the respective outside edges of the upper end of the handle so to form blow moulded lugs adjacent the respective edges of the handle at its upper end. Such blow moulded lugs will also co-operate to resist rotational movement of the handle. The lower retaining means of the handle is preferably a lug or protrusion extending from the lower end of the handle. It should be shaped so that on blow moulding of the preform expansion of the side wall will capture and secure the lug within the formed body of the container. It may be of various geometrical shapes. Most preferably, a lug which incorporates a hook or other extension is utilised so to encourage secure engagement with the body of the container.
The handle may be of any suitable configuration. In one embodiment of the invention, the container formed is blow moulded so to include a recess on one side suitable for accommodating the handle. Preferably, this recess includes a ledge onto which the bottom part of the handle may rest. In this configuration, it is preferred that the handle be generally xe2x80x9cCxe2x80x9d shaped in configuration with the upper and lower retaining means being at opposite ends. In a particularly preferred embodiment, the cross section of the handle is xe2x80x9cUxe2x80x9d shaped so to include terminal flanges and a connecting web. It is preferred that the terminal flanges face downwardly at the lower end of the handle so that a hollow is formed under the connecting web. In this embodiment, the lower retaining means may be a lug extending from the web. When configured in this way, blow moulding of the preform in the vicinity of the lug forms a container side wall which fills the hollow formed by the flanges underneath the connecting web and thus securely retains the lug in position.
The handle may also include reinforcing ribs. In the embodiment described above in which the handle has terminal flanges extending from a web so to create a hollow on the underside of the handle, it is preferred to strengthen the terminal flanges with ribbing, as this area is exposed to high forces exerted by the expanding side wall of the preform during the blow moulding process.
Preferably, the handle is formed by injection moulding. It is not necessary that it be made from the same material as the container and it may be formed from a plastic such as high density polyethylene, polypropylene, PET, recycled PET, glass reinforced PET or glass reinforced high density polyethylene. The handle may also be made from metals such as aluminium. The container and the handle are preferably made from the same material. Most preferably this is PET or recycled PET. The use of the same materials for both container and handle simplifies recycling of the combination.
The preform used in the present invention may be made from any stretch blow mouldable polymer. Preferably, it is formed from a PET homopolymer or copolymer (whether virgin or regrind) or is a multi-layer structure which may include layers consisting of one or more of PET, PEN, EVOH or other polymers used in multilayer technology.
In accordance with a further embodiment of the invention, there is provided a handled plastic container which includes a blow moulded plastic bottle which has an external flange proximate to its opening and a separate handle interconnected thereto, wherein said handle includes an upper end and a depending gripping portion, the said upper end of the handle being fixedly connected to the container being sandwiched between the underside of the external flange and a portion of the container side wall.
Preferably, the upper end of the handle includes a curved face shaped to follow the geometry of the preform immediately beneath the external flange. The curved face is provided
In a still further alternative embodiment, the upper end of the handle has a diverging distal end which is spaced below the flange and integrated with an upper dome portion of the container.
These and other features of the present invention will be understood from the following detailed description and drawings.